1. Field of the Invention
The present invention relates to a fastening element feeding device for a power drive-in tool and which includes a first component connectable with the power drive-in tool and a second component displaceably supported on the first component and having a head applicable against a constructional component, and a transportation device for feeding fastening elements arranged in a magazine strip in a drive-in channel. The transportation device includes a transportation wheel for the magazine strip and rotatably supported on a rotary axle, at least one actuation member displaceable in a control track in a first component for effecting a relative displacement between the first component and the second component which results in a transportation displacement of the transportation wheel.
2. Description of the Prior Art
Fastening element feeding devices for power drive-in tools such as, e.g., screwdriving power tools have a head that is placed on a constructional component and serves for guiding fastening elements such as, e.g., screws before and during a setting process. The head can be formed, e.g., as a part of a magazine with fastening elements or of a fastening element transportation device that is mountable on a flange of a drive-in tool.
German Utility Model DE 203 09 492 U1 discloses a screwdriving power tool with a screw feeding device having a first component in form of a holder that is mounted on a flange of the tool housing. A second component of the screwdriving tool in form of a screw guide is arranged on the first component with a possibility of displacement relative thereto, with the end of the screw guide, which faces in the operational direction, being placeable against a constructional component. On the second component, there is provided a rotatable disc on which a pawl is arranged. The pawl has an arm that projects from the rotatable disc and has a fixation pin on its end remote from the disc. The fixation pin extends through curved opening in a drive block and extends through a guideway in the holder. When the screw guide is displaced, upon the screwdriving tool being pressed against a constructional component, into the holder, the fixation pin is displaced along the guideway, with the pawl being rotated by the arcuate curved opening in the drive block. Thereby, the screws are fed through the screw guide and toward the screwdriving working tool.
The drawback of the above-described feeding device consists in the arrangement of the curve guide that curves with respect to the rotating disc and extends substantially transverse to the operational axis which is defined by the screwdriving working tool, which unfavorably influences the kinematics of the transport mechanism and leads to jamming and soiling of the curved guide. In addition, for starting the press-on process, a high press-on force, which is applied by the user, is needed for transportation of the screws.
German Publication DE 25 41 046 A1 discloses a power tool for screwing screws in, in which a slide is displaceably supported in the tool housing. In the slide, there is arranged a device for a stepwise transportation of screws in a screw-in position. The transportation device includes a ratchet wheel with two ratchet discs and a clutch disc. The clutch disc has projections that engage in corresponding recesses in the ratchet disc and are retained there by a biasing force. On the clutch disc, there is further provided a pin displaceable in a guide slot in the tool housing and in a slot in the slide. Upon the front end of the slide being pressed against a workpiece, the pin and the clutch disc connected therewith are rotated in the clockwise direction as a result of the positive guidance. This causes displacement of the strip with screws and feeding of a screw to the screw-in position. Upon lifting of the slide off the constructional component, the pin is displaced in the opposite direction, with a pawl preventing rotation of the ratchet discs in the counterclockwise direction. As a result, the clutch disc with the projections disengages from the ratchet disc against a spring biasing force and displaces alone in the counterclockwise direction to its initial position.
The drawback here, as in the German Utility Model DE 203 09 492 U1, consists in that for starting the press-on process, a high press-on force, which is applied by the user, is needed for transportation of the screws. Also, the transportation mechanism is susceptible to soiling and the resulting therefrom, failures.
German Patent DE 42 19 095 C1 discloses a displacement device with a ratchet wheel for a drive-in tool in which the ratchet wheel is supported on an end of a first arm of a two-arm pivotal lever, with the control pin being supported on the second arm. The two-arm pivotal lever in supported on a drag bearing arranged between the first and second arms. Upon a stop of the slide being pressed against a workpiece, the pivotal lever pivots, as a result of a positive guidance, in the clockwise direction, together with the ratchet wheel. The ratchet wheel is stopped by a stop catch and does not pivot further but still transports further screw strip. Upon the drive-in tool being lifted off the workpiece, the slide is pushed out of the housing by a spring, and the positively guided pin pivots the pivotal lever in the counterclockwise direction, with the rungs of the ratchet wheel still engaging in rim recesses of the screw strip.
The drawback of the displacement device of the German Patent consists in that the pivotal lever is very sensitive to soiling which can adversely affect its function.
Accordingly an object of the present invention is to provide a fastening element feeding device for a power drive-in tool in which the drawbacks of the known feeding devices are eliminated.
Another object of the present invention is a fastening element feeding device for a power drive-in tool and which has a simplified construction and provides for a reliable transportation of the screw strip.